Cell access procedure

ABSTRACT

A method comprising: detecting at a device associated with a first public land mobile network, a cell; receiving, for each of a plurality of public land mobile networks supported by the cell, an indication as to whether or not the cell is available for standalone access for that public land mobile network; and determining, in dependence upon the indications and based on the first public land mobile network, whether to request standalone access of the cell.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/045,455, filed Oct. 5, 2020, which is a national phase entry ofInternational Application No. PCT/FI2018/050245, filed Apr. 5, 2018, theentire contents of which are incorporated herein by reference.

FIELD

The present application relates to a method, apparatus, system andcomputer program. In particular, but not exclusively, the presentapplication relates to determining whether to perform an accessprocedure in a cell in dependence upon whether or not the cell supportsstandalone access for a public land mobile network of a device.

BACKGROUND

A communication system can be seen as a facility that enablescommunication sessions between two or more entities such as userterminals, base stations and/or other nodes by providing carriersbetween the various entities involved in the communications path. Acommunication system can be provided, for example, by means of acommunication network and one or more compatible communication devices.The communication sessions may comprise, for example, communication ofdata for carrying communications such as voice, video, electronic mail(email), text message, multimedia and/or content data and so on.Non-limiting examples of services provided comprise two-way or multi-waycalls, data communication or multimedia services and access to a datanetwork system, such as the Internet.

In a wireless communication system, at least a part of a communicationsession between at least two stations occurs over a wireless link.Examples of wireless systems comprise public land mobile networks(PLMN), satellite based communication systems and different wirelesslocal networks, for example wireless local area networks (WLAN). Thewireless systems can typically be divided into cells, and are thereforeoften referred to as cellular systems.

A user can access the communication system by means of an appropriatecommunication device or terminal. A communication device of a user maybe referred to as user equipment (UE) or user device. A communicationdevice is provided with an appropriate signal receiving and transmittingapparatus for enabling communications, for example enabling access to acommunication network or communications directly with other users. Thecommunication device may access a carrier provided by a station, forexample a base station of a cell, and transmit and/or receivecommunications on the carrier.

The communication system and associated devices typically operate inaccordance with a given standard or specification which sets out whatthe various entities associated with the system are permitted to do andhow that should be achieved. Communication protocols and/or parameterswhich shall be used for the connection are also typically defined. Oneexample of a communications system is UTRAN (3G radio). Other examplesof communication systems are the long-term evolution (LTE) of theUniversal Mobile Telecommunications System (UMTS) radio-accesstechnology and so-called 5G or New Radio (NR) networks. Standardizationof 5G or New Radio networks is currently under discussion. LTE is beingstandardized by the 3rd Generation Partnership Project (3GPP).

SUMMARY

According to a first aspect, there is provided a method comprising:detecting at a device associated with a first public land mobilenetwork, a cell; receiving, for each of a plurality of public landmobile networks supported by the cell, an indication as to whether ornot the cell is available for standalone access for that public landmobile network; and determining, in dependence upon the indications andbased on the first public land mobile network, whether to requeststandalone access of the cell.

In some embodiments, the cell is available for standalone access forsome of the plurality of public land mobile networks; and the cell isunavailable for standalone access for some of the plurality of publicland mobile networks.

In some embodiments, the method comprises, if the indications indicatethat the cell is available for standalone access for the first publicland mobile network, requesting standalone access for the cell.

In some embodiments, at least prior to requesting standalone access forthe cell, the device is in IDLE mode.

In some embodiments, the method comprises, if the indications indicatethat the cell is unavailable for standalone access for the first publicland mobile network, accessing the cell in dual connectivity mode.

In embodiment, the method comprises receiving from the base station, asystem information block comprising the indications as to whether or notthe cell is available for standalone access for the plurality of publicland mobile networks.

In some embodiments, wherein for at least one of the plurality of publicland mobile networks, the indication comprises a presence or absence ofa tracking area code.

In some embodiments, wherein for at least one of the plurality of publicland mobile networks, the indication comprises a binary indicator in afield of tracking area code information.

In some embodiments, wherein, for at least one of the plurality ofpublic land mobile networks, the indication comprises a binary indicatorin cell access related information. According to a second aspect, thereis provided a method comprising: for each of a plurality of public landmobile networks supported by a cell, causing a transmission to a deviceof an indication as to whether or not the cell is available forstandalone access of that public land mobile network.

In some embodiments, wherein the cell is available for standalone accessfor some of the plurality of public land mobile networks; and the cellis unavailable for standalone access for some of the plurality of publicland mobile networks.

In some embodiments, the method comprises, if the indication indicatesthat the cell is available for standalone access for a first public landmobile network supported by the device, receiving a request forstandalone access for the cell from the device.

In some embodiments, the method comprises if the indication indicatesthat the cell is unavailable for standalone access for a first publicland mobile network supported by the device, receiving a request fornon-standalone access of the cell from the device.

In some embodiments, the method comprises causing the transmission tothe device of a system information block comprising the indications asto whether or not the cell is available for standalone access for theplurality of public land mobile networks.

In some embodiments, for at least one of the plurality of public landmobile networks, the indication comprises a presence or absence of atracking area code.

In some embodiments, for at least one of the plurality of public landmobile networks, the indication comprises a binary indicator in a fieldof tracking area code information.

In some embodiments, for at least one of the plurality of public landmobile networks, the indication comprises a binary indicator in cellaccess related information.

According to a third aspect, there is provided a computer programcomprising instructions such that when the computer program is executedon a computing device provides a method, the computing device isarranged to perform the steps of either the first aspect or the secondaspect.

According to a fourth aspect, there is provided an apparatus comprising:at least one processor and at least one memory including a computerprogram code, the at least one memory and the computer program codeconfigured to, with the at least one processor, cause the apparatus atleast to: detect at a device associated with a first public land mobilenetwork, a cell; receive, for each of a plurality of public land mobilenetworks supported by the cell, an indication as to whether or not thecell is available for standalone access for that public land mobilenetwork; and determine, in dependence upon the indications and based onthe first public land mobile network, whether to request standaloneaccess of the cell.

In some embodiments, the cell is available for standalone access forsome of the plurality of public land mobile networks; and the cell isunavailable for standalone access for some of the plurality of publicland mobile networks.

In some embodiments, the apparatus is configured to, if the indicationsindicate that the cell is available for standalone access for the firstpublic land mobile network, request standalone access for the cell.

In some embodiments, at least prior to requesting standalone access forthe cell, the device is in IDLE mode.

In some embodiments, the apparatus is configured to, if the indicationsindicate that the cell is unavailable for standalone access for thefirst public land mobile network, access the cell in dual connectivitymode.

In some embodiments, the apparatus is configured to receive from thebase station, a system information block comprising the indications asto whether or not the cell is available for standalone access for theplurality of public land mobile networks.

In some embodiments, for at least one of the plurality of public landmobile networks, the indication comprises a presence or absence of atracking area code.

In some embodiments, for at least one of the plurality of public landmobile networks, the indication comprises a binary indicator in a fieldof tracking area code information.

In some embodiments, for at least one of the plurality of public landmobile networks, the indication comprises a binary indicator in cellaccess related information.

According to a fifth aspect, there is provided an apparatus comprising:at least one processor and at least one memory including a computerprogram code, the at least one memory and the computer program codeconfigured to, with the at least one processor, cause the apparatus atleast to for each of a plurality of public land mobile networkssupported by a cell, cause a transmission to a device of an indicationas to whether or not the cell is available for standalone access of thatpublic land mobile network.

In some embodiments, the cell is available for standalone access forsome of the plurality of public land mobile networks; and the cell isunavailable for standalone access for some of the plurality of publicland mobile networks.

In some embodiments, the apparatus is configured to, if the indicationindicates that the cell is available for standalone access for a firstpublic land mobile network supported by the device, receive a requestfor standalone access for the cell from the device.

In some embodiments, the apparatus configured to, if the indicationindicates that the cell is unavailable for standalone access for a firstpublic land mobile network supported by the device, receive a requestfor non-standalone access of the cell from the device.

In some embodiments, the apparatus is configured to cause thetransmission to the device of a system information block comprising theindications as to whether or not the cell is available for standaloneaccess for the plurality of public land mobile networks.

In some embodiments, for at least one of the plurality of public landmobile networks, the indication comprises a presence or absence of atracking area code.

In some embodiments, for at least one of the plurality of public landmobile networks, the indication comprises a binary indicator in a fieldof tracking area code information.

In some embodiments, for at least one of the plurality of public landmobile networks, the indication comprises a binary indicator in cellaccess related information.

According to a sixth aspect, there is provided an apparatus comprising:means for detecting at a device associated with a first public landmobile network, a cell; means for receiving, for each of a plurality ofpublic land mobile networks supported by the cell, an indication as towhether or not the cell is available for standalone access for thatpublic land mobile network; and means for determining, in dependenceupon the indications and based on the first public land mobile network,whether to request standalone access of the cell.

According to a seventh aspect, there is provided an apparatuscomprising: means for, for each of a plurality of public land mobilenetworks supported by a cell, causing a transmission to a device of anindication as to whether or not the cell is available for standaloneaccess of that public land mobile network.

DESCRIPTION OF FIGURES

Some examples will now be described with reference to the accompanyingFigures in which:

FIG. 1 shows a schematic diagram of an example communication systemcomprising a base station and a plurality of communication devices;

FIG. 2 shows a schematic diagram of an example mobile communicationdevice;

FIG. 3 shows a schematic diagram of an example control apparatus;

FIG. 4 illustrates an example of a non-transitory computer readablemedium;

FIG. 5 shows an example communication system illustrating dualconnectivity;

FIG. 6 shows an example communication system illustrating the initialaccess procedure according to examples of the application;

FIG. 7 shows an example of a method that may be implemented in acommunication device; and

FIG. 8 shows an example of a method that may be implemented in a basestation or a control apparatus for a base station.

DETAILED DESCRIPTION

Before explaining in detail the examples, certain general principles ofa wireless communication system and mobile communication devices arebriefly explained with reference to FIGS. 1 to 2 to assist inunderstanding the technology underlying the described examples.

In a wireless communication system 100, such as that shown in FIG. 1,mobile communication devices or user equipment (UE) 102, 104, 105 areprovided wireless access via at least one base station or similarwireless transmitting and/or receiving node or point. Base stations aretypically controlled by at least one appropriate controller apparatus,so as to enable operation thereof and management of mobile communicationdevices in communication with the base stations. The controllerapparatus may be located in a radio access network (e.g. wirelesscommunication system 100) or in a core network (CN) (not shown) and maybe implemented as one central apparatus or its functionality may bedistributed over several apparatus. The controller apparatus may be partof the base station and/or provided by a separate entity such as a RadioNetwork Controller. In FIG. 1 control apparatus 108 and 109 are shown tocontrol the respective macro level base stations 106 and 107. Thecontrol apparatus of a base station can be interconnected with othercontrol entities. The control apparatus is typically provided withmemory capacity and at least one data processor. The control apparatusand functions may be distributed between a plurality of control units.In some systems, the control apparatus may additionally or alternativelybe provided in a radio network controller.

In FIG. 1, base stations 106 and 107 are shown as connected to a widercommunications network 113 via gateway 112. A further gateway functionmay be provided to connect to another network.

The smaller base stations 116, 118 and 120 may also be connected to thenetwork 113, for example by a separate gateway function and/or via thecontrollers of the macro level stations. The base stations 116, 118 and120 may be pico or femto level base stations or the like. In theexample, stations 116 and 118 are connected via a gateway 111 whilststation 120 connects via the controller apparatus 108. In someembodiments, the smaller stations may not be provided. Smaller basestations 116, 118 and 120 may be part of a second network, for exampleWLAN and may be WLAN APs.

An example of wireless communication systems are architecturesstandardized by the 3rd Generation Partnership Project (3GPP). A 3GPPbased development is often referred to as the long term evolution (LTE)of the Universal Mobile Telecommunications System (UMTS) radio-accesstechnology. The various development stages of the 3GPP specificationsare referred to as releases. More recent developments of the LTE areoften referred to as LTE Advanced (LTE-A). The LTE employs a mobilearchitecture known as the Evolved Universal Terrestrial Radio AccessNetwork (E-UTRAN). Base stations of such systems are known as evolved orenhanced Node Bs (eNBs) and provide E-UTRAN features such as user planePacket Data Convergence/Radio Link Control/Medium AccessControl/Physical layer protocol (PDCP/RLC/MAC/PHY) and control planeRadio Resource Control (RRC) protocol terminations towards thecommunication devices. Other examples of radio access system comprisethose provided by base stations of systems that are based ontechnologies such as wireless local area network (WLAN) and/or WiMax(Worldwide Interoperability for Microwave Access). A base station canprovide coverage for an entire cell or similar radio service area.

An example of a suitable communications system is the 5G or NR concept.Network architecture in NR may be similar to that of LTE-advanced. Basestations of NR systems may be known as next generation Node Bs (gNBs).Changes to the network architecture may depend on the need to supportvarious radio technologies and finer QoS support, and some on-demandrequirements for e.g. QoS levels to support QoE of user point of view.Also network aware services and applications, and service andapplication aware networks may bring changes to the architecture. Thoseare related to Information Centric Network (ICN) and User-CentricContent Delivery Network (UC-CDN) approaches. NR may use multipleinput-multiple output (MIMO) antennas, many more base stations or nodesthan the LTE (a so-called small cell concept), including macro sitesoperating in co-operation with smaller stations and perhaps alsoemploying a variety of radio technologies for better coverage andenhanced data rates.

Future networks may utilise network functions virtualization (NFV) whichis a network architecture concept that proposes virtualizing networknode functions into “building blocks” or entities that may beoperationally connected or linked together to provide services. Avirtualized network function (VNF) may comprise one or more virtualmachines running computer program codes using standard or general typeservers instead of customized hardware. Cloud computing or data storagemay also be utilized. In the context of radio communications, this maymean that node operations are carried out, at least partly, in acentral/centralized unit, CU, (e.g. server, host or node) operationallycoupled to a distributed unit, DU, (e.g. a radio head/node). It is alsopossible that node operations will be distributed among a plurality ofservers, nodes or hosts. It should also be understood that thedistribution of labour between core network operations and base stationoperations may differ from that of the LTE or even be non-existent. Inan embodiment, the server may generate a virtual network through whichthe server communicates with the radio node. In general, virtualnetworking may involve a process of combining hardware and softwarenetwork resources and network functionality into a single,software-based administrative entity, a virtual network. Such virtualnetwork may provide flexible distribution of operations between theserver and the radio head/node. In practice, any digital signalprocessing task may be performed in either the CU or the DU and theboundary, where the responsibility is shifted between the CU and the DU,may be selected according to the specific implementation.

A possible mobile communication device will now be described in moredetail with reference to FIG. 2 showing a schematic, partially sectionedview of a communication device 200. Such a communication device is oftenreferred to as a user equipment (UE) or terminal. An appropriate mobilecommunication device may be provided by any device capable of sendingand receiving radio signals. Non-limiting examples comprise a mobilestation (MS) or mobile device such as a mobile phone or what is known asa ‘smart phone’, a computer provided with a wireless interface card orother wireless interface facility (e.g., USB dongle), personal dataassistant (PDA) or a tablet provided with wireless communicationcapabilities, or any combinations of these or the like. A mobilecommunication device may provide, for example, communication of data forcarrying communications such as voice, electronic mail (email), textmessage, multimedia and so on. Users may thus be offered and providednumerous services via their communication devices. Non-limiting examplesof these services comprise two-way or multi-way calls, datacommunication or multimedia services or simply an access to a datacommunications network system, such as the Internet. Users may also beprovided broadcast or multicast data. Non-limiting examples of thecontent comprise downloads, television and radio programs, videos,advertisements, various alerts and other information.

The communication devices 102, 104, 105 may access the communicationsystem based on various access techniques, such as code divisionmultiple access (CDMA), or wideband CDMA (WCDMA). Other non-limitingexamples comprise time division multiple access (TDMA), frequencydivision multiple access (FDMA) and various schemes thereof such as theinterleaved frequency division multiple access (IFDMA), single carrierfrequency division multiple access (SC-FDMA) and orthogonal frequencydivision multiple access (OFDMA), space division multiple access (SDMA)and so on.

The mobile device 200 may receive signals over an air or radio interface207 via appropriate apparatus for receiving and may transmit signals viaappropriate apparatus for transmitting radio signals. In FIG. 2,transceiver apparatus is designated schematically by block 206. Thetransceiver apparatus 206 may be provided for example by means of aradio part and associated antenna arrangement. The antenna arrangementmay be arranged internally or externally to the mobile device.

A mobile device is typically provided with at least one data processingentity 201, at least one memory 202 and other possible components 203for use in software and hardware aided execution of tasks it is designedto perform, including control of access to and communications withaccess systems and other communication devices. The data processing,storage and other relevant control apparatus can be provided on anappropriate circuit board and/or in chipsets. This feature is denoted byreference 204. The user may control the operation of the mobile deviceby means of a suitable user interface such as key pad 205, voicecommands, touch sensitive screen or pad, combinations thereof or thelike. A display 208, a speaker and a microphone can be also provided.Furthermore, a mobile communication device may comprise appropriateconnectors (either wired or wireless) to other devices and/or forconnecting external accessories, for example hands-free equipment,thereto.

FIG. 3 shows an example of a control apparatus for a communicationsystem, for example to be coupled to and/or for controlling a station ofan access system, such as a RAN node, e.g. a base station, (e) node B or5G AP, or a node of a core network such as an MME or S-GW, or a serveror host. The method may be implemented in a single control apparatus oracross more than one control apparatus. The control apparatus may beintegrated with or external to a node or module of a core network orRAN. In some embodiments, base stations comprise a separate controlapparatus unit or module. In other embodiments, the control apparatuscan be another network element such as a radio network controller or aspectrum controller. In some embodiments, each base station may havesuch a control apparatus as well as a control apparatus being providedin a radio network controller. The control apparatus 300 can be arrangedto provide control on communications in the service area of the system.The control apparatus 300 comprises at least one random access memory310, at least one read only memory 350 at least one data processing unit320, 330 and an input/output interface 340. Via the interface, thecontrol apparatus can be coupled to a receiver and a transmitter of thebase station. The receiver and/or the transmitter may be implemented asa radio front end or a remote radio head.

Different possibilities regarding the deployment of cells in a networkexist. A cell may be deployed in a standalone deployment in which a cellmay be accessed by devices operating in IDLE mode. In standalone mode,an IDLE device may initiate and complete an initial access procedure, inwhich the device accesses the cell to initiate data transfer. Theinitial access procedure may include cell search and selection, thereceipt from the base station of the cell of system information, and theperforming of a random access procedure to access the cell.

The system information that is received from the base station at thecommunication device may include one or more information blocks. In LTE,after the cell selection has taken place, the device is configured toreceive a Master Information Block (MIB) from the eNodeB. The MIBincludes an indication of the system bandwidth and information relatedto the Physical Hybrid-ARQ Indicator Channel (PHICH), which carries, inthe downlink, Hybrid ARQ (HARQ) acknowledgements (ACK/NACK) for uplinkdata transfers. Following the receipt of the MIB, the device receivesfrom the eNB, a series of system information blocks. These are numberedconsecutively from 1 to 22. There are 22 SIBs (SIB1 to SIB22-NB) in the3GPP E-UTRA standard specification. Each SIB contains specificinformation. SIB1 means System Information Block Type 1. SIB1 includesan indication of the cell ID, scheduling information for the remainingSIBs and cell access related information, which is required by the UE toaccess the cell. Since the 3GPP NR specification is not finalized, thetotal number of SIBs in NR is not yet known. However, according to thecurrent 3GPP agreements, SIB1 in NR will contain information similar tothe one mentioned above for E-UTRA, but with differences resulting fromthe specificities of NR.

A cell may be deployed in non-standalone mode (NSA), in which the cellcan only be accessed in dual connectivity mode. For example, in socalled option 3, a new radio (NR) cell supporting NSA can only be addedto the UE as part of a SCG (Secondary Cell Group) in E-UTRA-NR DualConnectivity (EN-DC) mode such that an LTE cell is part of the MasterCell Group (MCG). Other NSA options include, for example, option 4(where the NR cell is part of the MCG, while the LTE cell is part of theSCG), and option 7 (where again the LTE is part of the MCG and the NRcell is part of the SCG, but they are both connected to the 5G CoreNetwork, instead of the LTE core network (Evolved Packet Core) as inoption 3). The base station of an NSA cell (which is part of a secondarycell group) in option 3 may be a secondary base station (also referredto as a Secondary Node (SN)) that provides additional radio resources toa device.

Reference is made to FIG. 5, which shows an example communication system500 illustrating the standalone and non-standalone deployment scenariosfor cells. In the Figure, the solid line between the components of thesystem indicates the data plane. On the other hand, the dashed lineindicates the control plane. The communication system 500 includes acommunication device 510 (e.g. a UE) that is configured to communicatewith a first base station 520. The first base station 520 may be anEnodeB (in LTE) or a gNodeB (in New Radio). The first base station 520is configured to communicate with the core network 540, by exchangingdata and control information. The core network 540 may belong to a firstPLMN and may serve devices associated with the first PLMN. In thisexample, the first device is associated with the first PLMN. Since, thefirst base station 520 exchanges control information directly with thecore network 540 it is able to act as a master base station for thedevices associated with the first PLMN. The first base station 520therefore provides cells deployed in standalone mode for the devicesassociated with the first PLMN, and the device 510 is able to accessthese cells when in IDLE mode via an initial access procedure which itinitiates with the first base station 520. Since, these cells aredeployed in standalone mode, the device 510 may in some examples connectwith the first base station 520 only, instead of operating in dualconnectivity mode.

In the example shown in FIG. 5, the communication device 510 isconfigured to operate in dual connectivity mode in which it has twoseparate connections to different base stations. A second base station530 is shown in the figure which is also in communication with thedevice 510. The second base station 530 may exchange data directly withthe core network 540. However, the second base station 530 does notexchange control information directly with the core network 540. Rather,the second base station 530 exchanges control information with the firstbase station 520. The first base station 520 exchanges control and datainformation with the core network 540 and acts as a mobility anchortowards the core network 540. The data and control information exchangedbetween the first base station 510 and the second base station 520 maybe exchanged via a backhaul communication link between the first basestation 510 and the second base station 520. The second base station530, therefore, acts as a secondary base station, which provides asecondary cell group, for the devices associated with the first PLMN.The cells of the secondary cell group may be said to be deployed innon-standalone mode. In an embodiment, the base stations 520 and 530 maybe co-located as a single base station providing two (or more) cells.Out of these cells, some may support for the standalone access whilesome others may not support standalone access (i.e. supportnon-standalone access).

The communication device 510 may access the cells provided by thesecondary base station 530 only when in dual connectivity with the firstbase station 520 as well as the secondary base station 530. Since thedevice 510 is configured to connect to a cell of the first base station520 prior to connecting to a cell of the second base station, there isno need to perform the initial access procedure described above whenconnected to a cell of the second base station. The device 510 is unableto access them using the initial access procedure since the cells of thesecond base station 530 are not configured for operation in thestandalone mode for the first PLMN.

Therefore, in the example given in FIG. 5 cells of a communicationsystem may be deployed in a standalone mode or non-standalone mode.

One issue that may arise is that if the device 510 is unaware of whichcells are configured for standalone operation and which cells areconfigured for non-standalone operation, the device may repeatedly makeinitial access requests for cells that are not configured for standaloneoperation. Therefore, these requests keep on being rejected by thenetwork. This may be inefficient for the devices, which use batterypower by sending the requests. It may also be inefficient for thenetwork due to the additional signalling incurred on air interface andon network interfaces.

One proposed solution to this problem is to exclude from the informationtransmitted by the base station, information required by the device forsending the access requests. This may comprise excluding the SIB1 fromthe System Information transmissions made by the base station during theinitial access procedure described above. The absence of the SIB1 may beindicated in the MIB that is received at the device from the basestation. Alternatively, it could comprise transmitting the SIB1, butwith the information required for the UE to perform initial accessattempt omitted. In this case, the SIB1 may still include theinformation (e.g. so called cell access related information) that isrequired for the Automatic Neighbour Relation (ANR) function.

In ANR, each cell detects its neighbour and updates its neighbour celllist automatically. Since a cell does not have the measurementfunctionality to detect the existence of its neighbouring cells, the UEconnected to a cell can be instructed by the base station to detect thecells around it and report this to the base station. The proposedmodified SIB1 may omit the information required for the initial accessprocedure but retain the cell access related information that isrequired for performing the ANR function.

By omitting the SIB1 (or certain information from the SIB1), an IDLEmode device will not attempt to access the cell, since the informationrequired for initial access will be missing. Only minimum informationfor ANR purposes may be provided.

In some cases, for a communication system, network sharing may beimplemented. In this case, two or more operators share parts of thenetwork infrastructure to improve economies of scale. For example, theradio access network, cell sites and backhaul transport may be shared bytwo or more operators. The core network equipment may remain dedicatedto each operator. As a result, each operator may establish and operateits own public land mobile network (PLMN). Since, the core network maybelong to a specific PLMN, whilst the base stations may be sharedamongst PLMNs, the situation may arise that a particular cell of thecommunication system may be available for standalone access for somePLMNs, whilst only available for non-standalone access for other PLMNs.If the proposed solution described above (i.e. omitting the SIB1 oromitting the information required for the initial access procedure fromtransmission) is applied in this context, then the device may nottransmit the access requests even if the cell is available forstandalone access for the PLMN of the device, whilst not being availablefor standalone access for PLMNs of other devices. Hence, the proposaldescribed above is not ideal for network sharing scenarios. Examples ofthe application may address these problems.

Reference is made again to FIG. 5, which in addition to the core network540, also shows core network 550. The core network 540 belongs to afirst PLMN, whilst the core network 550 belongs to a second PLMN. Thecore network 540 could be an Evolved Packet Core. The core network 550could be a 5G core network. The core network 550 is connected to asecond base station 530 and is configured to exchange data and controlinformation with the second base station 530. As a result, the cellsprovided by the second base station are deployed in standalone mode forthe second PLMN. Any communication devices that are associated with thesecond PLMN will be able to access the cells of the second base stationin standalone mode. However, communication devices associated with thefirst PLMN, such as device 510, will only be able to access the cells innon-standalone mode. Therefore, as a result of network sharing, a cellmay provide standalone access for some PLMNs, but not for others.Therefore, the problems associated with omitting the SIB1 in full orpart, as described above, may occur.

According to examples of the application, the base station transmits tothe communication device, for each of a plurality of PLMNs supported bya cell, an indication of whether or not the cell is available forstandalone access for that PLMN. The device is configured to use theseindications to determine whether or not to transmit an access requestfor standalone access of the cell. The device is configured to support aspecific PLMN. If the device receives an indication that the PLMN thatit supports is available for standalone access for the cell, the devicetransmits one or more access requests for standalone access.

If the device receives an indication that the PLMN that it supports isunavailable for standalone access, in some examples, the device mayaccess the cell in dual connectivity mode. In the dual connectivitymode, the device may also be in communication with a further cell (amaster cell). The cell for which it receives the indication may bedeployed in non-standalone mode and may act as a secondary cell for thedevice. To access a cell in non-standalone mode, another base station(e.g. a master base station) may add the cell to the Secondary CellGroup.

The indications as to whether or not the cell is available forstandalone access for the PLMNs may be included in the systeminformation that is transmitted by the base station. The indications maybe transmitted in the SIB1 that is described above. The structure of theSIB1, and examples of how the indications may be included therein, areshown in Annex A. The SIB1 contains information for evaluating if a UEis allowed to access a cell and defines the scheduling of other systeminformation. It also contains radio resource configuration informationthat is common for all UEs.

The device may receive the indications and determine whether the cellsupports standalone access for the PLMN that is supported by the device.If so, then the device may transmit an access request for standaloneaccess to the cell. The access request may be an initial access request.

Reference is made to FIG. 6, which illustrates an example communicationsystem 600 in which examples of the application may be implemented.

The examples communication system 600 includes a communication device610 and a base station 620. The base station 620 provides one or morecells. The communication device 610 detects one of the cells. The cellis configured to support a plurality of PLMNs. The device 610 operatesaccording to one of these PLMNs. The device 610 may be in IDLE modeprior to connecting with a cell. In an embodiment, the device 610detects a plurality of cells wherein each cell is configured to supporta plurality of PLMNs, and therefore each cell may be deployed as astandalone or non-standalone cell, based on the PLMN.

The base station 620 provides to the device 610, indications 640 as towhether or not standalone access to the cell is available for theplurality of PLMNs associated with a cell of the base station. Eachindication specifically indicates whether or not the standalone accessto the cell is available for a particular PLMN that is associated withthe cell.

The device 610 is configured to receive the indications 640 anddetermine, in dependence upon the indications and the PLMN supported bythe device, whether or not to transmit a request 650 for standaloneaccess to the base station 620. If the device 610 determines thatstandalone access to the cell is available for the PLMN that itsupports, the device transmits a request 650 for standalone access tothe base station 620.

If the device determines that standalone access is unavailable for thePLMN that it supports, the device does not transmit a request 650 forstandalone access to the base station 620. The device 610 may determinefrom the indications that the cell is available for non-standaloneaccess for the PLMN that it supports. In this case, the device 610 mayaccess the cell in non-standalone mode. The device 610 may access thecell in non-standalone mode if it determines from the indications thatthe cell is available for non-standalone mode and not available forstandalone mode for the PLMN which the device supports. Accessing thecell in non-standalone mode involves accessing the cell in dualconnectivity. The device 610 may, therefore, connect to both the cell ofthe base station 620 and another cell. The other cell may be a cell of afurther base station 630. The other cell may be part of a master cellgroup, with the cell for which the indications are received may be partof secondary cell group.

Reference is made to FIG. 7, which shows an example of a method 700 thatmay be performed in a communication device, e.g. device 610. The devicemay be a UE.

At S710, the device is configured to detect a cell supporting aplurality of PLMNs.

At S720, the device is configured to receive an indication for each ofthe plurality of PLMNs supported by the cell as to whether or notstandalone access is available for a PLMN supported by the device.

At S730, the device is configured to determine whether or not standalone(SA) access is available for the PLMN supported by the device. Thisdetermination is made based on an indication received for that PLMN atS720.

If standalone access is available for the PLMN supported by the device,the method 700 proceeds to S740, where the method 700 comprises causingthe device to transmit a request for standalone access to the basestation providing the cell.

If standalone access is unavailable for the PLMN supported by thedevice, at S750, the device does not transmit a request for standaloneaccess for the cell. The method may proceed to S760, where the deviceaccesses the cell in dual connectivity mode.

At S760, to access the cell in dual connectivity mode, the device may beaccessing a second cell (part of a master cell group) in standaloneaccess mode. The master base station transmits information to the deviceto permit the device to access the cell, for which standalone access isunavailable, in non-standalone mode. The information may comprise thesecondary cell group configuration. After receiving the information, thedevice may access cell in non-standalone mode.

Reference is made to FIG. 8, which illustrates an example of a method800 that may be performed in a base station or in a control apparatus ofthe base station. The base station provides at least one cell.

At S810, the method comprises causing the transmission of indicationsfor each PLMN supported by the cell as to whether or not standaloneaccess is available for that PLMN.

At S820, if standalone access is available for the PLMN supported by thedevice, the method proceeds to S830. On the other hand, if standaloneaccess is not available for the PLMN supported by the device, the methodproceeds to S840.

At S830, the base station receives from the device, a request forstandalone access for the cell.

At S840, the base station does not receive a request for standaloneaccess for the cell.

The method may proceed to S850, in which the cell is accessed by thedevice in dual connectivity mode. This may comprise the base stationreceiving and responding to a request for non-standalone access to thecell.

Without providing the indication of the present application, standalonecapable devices belonging to a PLMN that does not support for standaloneoperation for a particular cell may keep on attempting to access thatcell and will, therefore, keep on being rejected by the network. Thiswill unnecessarily waste battery power by sending those requests overthe network and waste radio resources due to the additional unnecessarysignalling incurred on the air interface and on the network interfaces.By providing the indications to the device, examples of the applicationmay address these issues.

It should be understood that each block of the flowcharts of FIGS. 7 and8, and any combination thereof may be implemented by various means ortheir combinations, such as hardware, software, firmware, one or moreprocessors and/or circuitry.

The methods may be implemented on a mobile device as described withrespect to FIG. 2 or control apparatus as shown in FIG. 3.

In one embodiment, the cell for which the indications are sent does notbelong to a closed subscriber group (CSG). In one embodiment, theindications from the cell are not related to CSG.

Control functions may comprise detecting at a device associated with afirst public land mobile network, a cell; receiving, for each of aplurality of public land mobile networks supported by the cell, anindication as to whether or not the cell is available for standaloneaccess for that public land mobile network; and determining, independence upon the indications and based on the first public landmobile network, whether to request standalone access of the cell.

Additionally or alternatively, control functions may comprise: for eachof a plurality of public land mobile networks supported by a cell,causing a transmission to a device of an indication as to whether or notthe cell is available for standalone access of that public land mobilenetwork.

It should be understood that the apparatuses may comprise or be coupledto other units or modules etc., such as radio parts or radio heads, usedin or for transmission and/or reception. Although the apparatuses havebeen described as one entity, different modules and memory may beimplemented in one or more physical or logical entities.

It is noted that whilst embodiments have been described in relation toLTE/LTE-A/New Radio, similar principles can be applied in relation toother networks and communication systems. For example, the principlesmay be applied to devices operating using multi-connectivity. Therefore,although certain embodiments were described above by way of example withreference to certain example architectures for wireless networks,technologies and standards, embodiments may be applied to any othersuitable forms of communication systems than those illustrated anddescribed herein.

It is also noted herein that while the above describes exampleembodiments, there are several variations and modifications which may bemade to the disclosed solution without departing from the scope of thepresent invention.

In general, the various embodiments may be implemented in hardware orspecial purpose circuits, software, logic or any combination thereof.Some aspects of the invention may be implemented in hardware, whileother aspects may be implemented in firmware or software which may beexecuted by a controller, microprocessor or other computing device,although the invention is not limited thereto. While various aspects ofthe invention may be illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it is wellunderstood that these blocks, apparatus, systems, techniques or methodsdescribed herein may be implemented in, as non-limiting examples,hardware, software, firmware, special purpose circuits or logic, generalpurpose hardware or controller or other computing devices, or somecombination thereof.

The embodiments of this invention may be implemented by computersoftware executable by a data processor of the mobile device, such as inthe processor entity, or by hardware, or by a combination of softwareand hardware. Computer software or program, also called program product,including software routines, applets and/or macros, may be stored in anyapparatus-readable data storage medium and they comprise programinstructions to perform particular tasks. A computer program product maycomprise one or more computer-executable components which, when theprogram is run, are configured to carry out embodiments. The one or morecomputer-executable components may be at least one software code orportions of it.

Further in this regard it should be noted that any blocks of the logicflow as in the Figures may represent program steps, or interconnectedlogic circuits, blocks and functions, or a combination of program stepsand logic circuits, blocks and functions. The software may be stored onsuch physical media as memory chips, or memory blocks implemented withinthe processor, magnetic media such as hard disk or floppy disks, andoptical media such as for example DVD and the data variants thereof, CD.The physical media is a non-transitory media. An example of anon-transitory computer readable medium 400 is shown in FIG. 4. Thenon-transitory computer readable medium 400 may be a CD or DVD.

The memory may be of any type suitable to the local technicalenvironment and may be implemented using any suitable data storagetechnology, such as semiconductor based memory devices, magnetic memorydevices and systems, optical memory devices and systems, fixed memoryand removable memory. The data processors may be of any type suitable tothe local technical environment, and may comprise one or more of generalpurpose computers, special purpose computers, microprocessors, digitalsignal processors (DSPs), application specific integrated circuits(ASIC), FPGA, gate level circuits and processors based on multi coreprocessor architecture, as non-limiting examples.

Embodiments of the inventions may be practiced in various componentssuch as integrated circuit modules. The design of integrated circuits isby and large a highly automated process. Complex and powerful softwaretools are available for converting a logic level design into asemiconductor circuit design ready to be etched and formed on asemiconductor substrate.

The foregoing description has provided by way of non-limiting examples afull and informative description of the exemplary embodiment of thisinvention. However, various modifications and adaptations may becomeapparent to those skilled in the relevant arts in view of the foregoingdescription, when read in conjunction with the accompanying drawings andthe appended claims.

However, all such and similar modifications of the teachings of thisinvention will still fall within the scope of this invention as definedin the appended claims. Indeed there is a further embodiment comprisinga combination of one or more embodiments with any of the otherembodiments previously discussed.

ANNEX A

The following provides an indication of the structure of the SIB1message and its constituent elements that may be used to indicate to adevice whether or not standalone access is supported by the cell forspecific PLMNs. Sections 1 to 5 illustrate the structure of a typicalSIB1 message. Sections 6 to 9 illustrate part of the structure of amodified SIB1 message that indicates whether or not the standaloneaccess is available for each PLMN.

For the SIB1 message, the following may apply:

RLC-SAP (Radio Link Control-Service Access Points): Transparent ModeLogical Channels: Broadcast Control Channel (BCCH) 1. SIB1 Message

The structure of an SIB1 message is as follows:

-- ASN1START -- TAG-SIB1-START SIB1 ::= SEQUENCE {multiFrequencyBandListNR MultiFrequencyBandListNR OPTIONAL, p-Max P-MaxOPTIONAL, cellSelectionInfo SEQUENCE { q-RxLevMin Q-RxLevMin, q-QualMinQ-Qualmin OPTIONAL -- Need N } OPTIONAL, cellAccessRelatedInfo SEQUENCE(SIZE (1..maxPLMN)) OF CellAccessRelatedInfo, cellReservedConfigCellReservedConfig OPTIONAL, ranAC RANNotificationAreaCode OPTIONAL,ac-BarringInfo AC-BarringInfo OPTIONAL, otherSI-Info OtherSI-InfoOPTIONAL, servingCellConfigCommon ServingCellConfigCommon OPTIONAL,ims-EmergencySupport ENUMERATED {true} OPTIONAL, eCallOverIMS-SupportENUMERATED {true} OPTIONAL, lateNonCriticalExtension OCTET STRINGOPTIONAL, nonCriticalExtension SEQUENCE{ } OPTIONAL } -- TAG-SIB1-STOP-- ASN1STOP

2. CellAccessRelatedInfo Element

The IE CellAccessRelatedInfo is, as shown above, part of the SIB1message, and indicates cell access related information for this cell.The structure is as follows:

-- ASN1START -- TAG-CELL-ACCESS-RELATED-INFO-START CellAccessRelatedInfoSEQUENCE { plmn-IdentityList PLMN-IdentityList, trackingAreaCodeTrackingAreaCode cellIdentity CellIdentity } -- TAG-CELL-ACCESS-RELATED-INFO-STOP -- ASN1STOP

3. PLMN-IdentityList

The PLMN-IdentityList is, as shown above, part of theCellAccessRelatedInfo, and provides a list of PLMN identities. Thestructure is shown below:

-- ASN1START -- TAG-PLMN-IDENTITY-LIST-START PLMN-IdentityList ::=SEQUENCE (SIZE (1..maxPLMN)) OF PLMN-IdentityInfo PLMN-Identitylnfo ::=SEQUENCE { plmn-Identity PLMN-Identity, ... } --TAG-PLMN-IDENTITY-LIST-STOP -- ASN1STOP

4. PLMN Identity Element

The PLMN-IdentityList comprises IE PLMN-Identity elements. EachPLMN-Identity element identifies a Public Land Mobile Network.

-- ASN1START -- TAG-PLMN-IDENTITY-START PLMN-Identity ::= SEQUENCE { mccMCC OPTIONAL, mnc MNC } MCC ::= SEQUENCE (SIZE (3)) OF MCC-MNC-Digit MNC::= SEQUENCE (SIZE (2..3)) OF MCC-MNC-Digit MCC-MNC-Digit ::= INTEGER(0..9) -- TAG-PLMN-IDENTITY-STOP -- ASN1STOP

5. CellIdentity Information Element

The IE CellIdentity is, as shown above, part of theCellAccessRelatedInfo, and is used to unambiguously identify a cellwithin a PLMN.

-- ASN1START CellIdentity ::= BIT STRING (SIZE (36)) -- ASN1STOPTrackingAreaCode ::= ENUMERATED {ffsTypeAndValue}

6. CellAccessRelatedInfo in Modified MIB1

As in the case of the typical SIB1, the IE CellAccessRelatedInfoindicates cell access related information for this cell. In this case,it provides a Tracking Area Code of the cell for PLMNs indicated inplmn-identityList. If absent for the PLMN to which the UE is registered,the UE should not attempt to access this cell. The structure of theCellAccessRelatedInfo may be given by:

-- ASN1START -- TAG-CELL-ACCESS-RELATED-INFO-START CellAccessRelatedInfoSEQUENCE { plmn-IdentityList PLMN-IdentityList, trackingAreaCodeTrackingAreaCode OPTIONAL, -- Need S cellIdentity CellIdentity } -- TAG-CELL-ACCESS-RELATED-INFO-STOP -- ASN1STOP

7. TrackingAreaCode in Modified MIB1

The tracking area code in CellAccessRelatedInfo may be specified in thefollowing way:

TrackingAreaCode CHOICE { trackingAreaCode BIT STRING (SIZE (24)),initialAccessNotAllowed NULL }

8. Alternative TrackingAreaCode in Modified SIB1

In some examples of the application, the tracking area code may beprovided in the SIB1 for cells configured for non-standalone accesscells. This may be included, for example, for a Handover RestrictionList. The tracking area code in CellAccessRelatedInfo may be specifiedin the following way:

TrackingAreaCode SEQUENCE { trackingAreaCode BIT STRING (SIZE (24)),initialAccessAllowed BOOLEAN }

9. Alternative CellAccessRelatedInfo in Modified MIB1

In some examples, an initial access allowed flag can be provideddirectly in the access related info. This is a Boolean value thatindicates for each PLMN whether standalone access is allowed or not. Thestructure is given by:

-- ASN1START -- TAG-CELL-ACCESS-RELATED-INFO-START CellAccessRelatedInfoSEQUENCE { plmn-IdentityList PLMN-IdentityList, trackingAreaCodeTrackingAreaCode, cellIdentity CellIdentity, initialAccessAllowedBOOLEAN } -- TAG- CELL-ACCESS-RELATED-INFO-STOP -- ASN1STOP

That which is claimed is:
 1. A method comprising: detecting a cell at auser equipment associated with a first public land mobile network of aplurality of public land mobile networks supported by the cell;receiving, at the user equipment for each of the plurality of publicland mobile networks supported by the cell, an indication as to whetherthe cell is available for standalone access for a corresponding one ofthe public land mobile networks; determining, at the user equipment andbased on the indication for the first public land mobile network,whether to request standalone access to the cell; in a case in which itis determined to request standalone access, performing a random accessprocedure to access the cell; and in a case in which it is determinednot to request standalone access, performing at least a cell search. 2.A method as claimed in claim 1, wherein the cell is available forstandalone access for some of the plurality of public land mobilenetworks; and the cell is unavailable for standalone access for some ofthe plurality of public land mobile networks.
 3. A method as claimed inclaim 1, further comprising, if the indications indicate that the cellis available for standalone access for the first public land mobilenetwork, requesting standalone access for the cell including performingthe random access procedure to access the cell.
 4. A method as claimedin claim 3, wherein at least prior to requesting standalone access forthe cell, the user equipment is in IDLE mode.
 5. A method as claimed inclaim 1, wherein in the case in which it is determined not to requeststandalone access, the method further comprises accessing the cell whenconfigured to operate in a dual connectivity mode.
 6. A method asclaimed in claim 1, wherein the indication comprises the presence orabsence of a tracking area code for the corresponding public land mobilenetwork.
 7. A method comprising: for each of a plurality of public landmobile networks supported by a cell, causing a transmission, from a basestation to a device, of an indication as to whether the cell isavailable for standalone access for a corresponding one of the publicland mobile networks; in a case in which standalone access is available,receiving a request from the device for access via a random accessprocedure; and in a case in which standalone access is not available,receiving a request from the device for non-standalone access.
 8. Amethod as claimed in claim 7, further comprising, if the indicationindicates that the cell is available for standalone access for a firstpublic land mobile network supported by the device, receiving a requestfor standalone access to the cell from the device including receivingthe request for access via the random access procedure.
 9. A method asclaimed in claim 7, wherein in the case in which standalone access isnot available, receiving the request for non-standalone access comprisesreceiving the request for non-standalone access with respect to thedevice configured to operate in a dual connectivity mode.
 10. A methodas claimed in claim 7, wherein the indication comprises the presence orabsence of a tracking area code for the corresponding public land mobilenetwork.
 11. An apparatus comprising: at least one processor and atleast one memory including a computer program code, the at least onememory and the computer program code configured to, with the at leastone processor, cause the apparatus at least to: detect a cell at a userequipment associated with a first public land mobile network of aplurality of public land mobile networks supported by the cell; receive,at the user equipment for each of the plurality of public land mobilenetworks supported by the cell, an indication as to whether the cell isavailable for standalone access for a corresponding one of the publicland mobile networks; determine, at the user equipment and based on theindication for the first public land mobile network, whether to requeststandalone access to the cell; in a case in which it is determined torequest standalone access, perform a random access procedure to accessthe cell; and in a case in which it is determined not to requeststandalone access, perform at least a cell search.
 12. An apparatus asclaimed in claim 11, wherein the cell is available for standalone accessfor some of the plurality of public land mobile networks; and the cellis unavailable for standalone access for some of the plurality of publicland mobile networks.
 13. An apparatus as claimed in claim 11,configured to, if the indications indicate that the cell is availablefor standalone access for the first public land mobile network, requeststandalone access to the cell comprising being configured to perform therandom access procedure to access the cell.
 14. An apparatus as claimedin claim 13, wherein at least prior to requesting standalone access forthe cell, the user equipment is in IDLE mode.
 15. An apparatus asclaimed in claim 11, configured to, if the indications indicate that thecell is unavailable for standalone access for the first public landmobile network, access the cell when configured to operate in dualconnectivity mode.
 16. An apparatus as claimed in claim 11, configuredto receive from a base station, a system information block comprisingthe indications as to whether the cell is available for standaloneaccess for the plurality of public land mobile networks.
 17. Anapparatus as claimed in claim 11, wherein, for at least one of theplurality of public land mobile networks, the indication comprises thepresence or absence of a tracking area code for the corresponding publicland mobile network.
 18. An apparatus comprising: at least one processorand at least one memory including a computer program code, the at leastone memory and the computer program code configured to, with the atleast one processor, cause the apparatus at least to: for each of aplurality of public land mobile networks supported by a cell, cause atransmission, from a base station to a device, of an indication as towhether the cell is available for standalone access for a correspondingone of the public land mobile networks; in a case in which standaloneaccess is available, receive a request from the device for access via arandom access procedure; and in a case in which standalone access is notavailable, receive a request from the device for non-standalone access.19. An apparatus as claimed in claim 18, wherein, in the case in whichstandalone access is not available, the at least one memory and thecomputer program code are configured to, with the at least oneprocessor, cause the apparatus to receive the request for non-standaloneaccess by receiving the request for non-standalone access with respectto the device configured to operate in a dual connectivity mode.
 20. Anapparatus as claimed in claim 18, wherein the indication comprises thepresence or absence of a tracking area code for the corresponding publicland mobile network.